doc: add documentation for socket.destroySoon()

PR-URL: #46337
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

doc/api/net.md

@@ -1024,6 +1024,16 @@ See [`writable.destroy()`][] for further details.
 
 See [`writable.destroyed`][] for further details.
 
+### `socket.destroySoon()`
+
+<!-- YAML
+added: v0.3.4
+-->
+
+Destroys the socket after all data is written. If the `'finish'` event was
+already emitted the socket is destroyed immediately. If the socket is still
+writable it implicitly calls `socket.end()`.
+
 ### `socket.end([data[, encoding]][, callback])`
 
 <!-- YAML